About the .NET Regex Tester
This is a free online tester for .NET regular expressions. Patterns run on the real
System.Text.RegularExpressions engine from .NET, compiled to WebAssembly with Blazor,
so the results match what your C# code will do.
Your data stays in your browser
All matching happens client-side. Your pattern and test text are never sent to a server. The app only remembers your last pattern, test strings and options in your browser's local storage.
Features
- Live results as you type, with matches highlighted in the test strings and color-coded capture groups (including named groups)
- All
RegexOptions: IgnoreCase, Multiline, Singleline, ExplicitCapture, IgnorePatternWhitespace, RightToLeft, CultureInvariant, ECMAScript, NonBacktracking and AnyNewLine Regex.SplitandRegex.Replacewith substitutions such as$1and${name}- Sample patterns, a clickable quick reference, copy buttons, and export of matches as JSON, CSV or text
- Light and dark themes
- A 2-second match timeout that stops runaway patterns (catastrophic backtracking) instead of freezing the page
Hosting
The pages are rendered to static HTML when the app is built, so the site is just files: HTML, CSS and the .NET runtime compiled to WebAssembly, served from Cloudflare's network. All the regex work is done by your browser.